Effects of Surface Oxidation on Cooling Characteristics during Quenching of Heated Metals in Subcooled Water

Abstract

The effect of surface oxidation on the cooling characteristics of silver, nickel, SUS304 stainless steel and pure iron cylindrical specimens during quenching in still subcooled water has been investigated. It is shown that the oxidation of specimen surface has very little effect on the cooling characteristics at the initial solid-liquid contact stage and the vapor blanket stage, but has a very strong influence on the characteristic temperature, i.e. the lower limit temperature of the vapor blanket stage. In general, surface oxidation causes the rise of the characteristic temperature, and this tendency is more remarkable for high subcooling of water. In particular, the presence of a thick layer of porous oxides on specimen surface results in the remarkable rise of the characteristic temperature. The characteristic temperature would be unaffected by surface wettability, but significantly affected by low thermal conductivity and roughness of oxide layer on specimen surface.